This invention relates generally to laminate switch assemblies wherein tensioned diaphragms provide a tactile indication of switch activation and, more particularly, to an improved switch activating diaphragm structure which includes a surrounding reinforcing collar to relieve the stresses created in the area between such diaphragms and adjacent planar portions of a diaphragm plate.
A large variety of printed circuit contact switches are available for use as information input keyboards. Such keyboards are used for an ever expanding number of products ranging from calculators to microwave ovens. Of the available switch varieties, many do not provide tactile feedback and, hence, may be unacceptable for some users.
An inexpensive way to form keyboards having tactile feedback is to deposit electrical contact patterns onto a printed circuit board and to provide a tensioned diaphragm or dome over each of the contact patterns. Electrically conducting pads which match the contact patterns on the circuit board are provided so that when a dome is depressed by an operator's finger, an associated pad contacts one of the deposited contact patterns to complete an electrical circuit through the contact pattern. Upon removal of the operating force, the tensioned dome springs back to its initial unoperated position to open the circuit through the contact pattern. The electrically conducting pads can be provided on the interior surface of the dome or can be provided on a separate contact sheet formed from insulating material.
Such switch assemblies form reliable electrical connections and provide tactile feedback to an operator to reassure the operator that the switch contact has been closed. Although keyboards formed from such switches are highly reliable, there tend to be problems in that the domes or diaphragms are formed into sheets of plastic material and, hence, are subject to deterioration with use.